<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>grid3</title>
    <style>
        .Site {
            display: flex;
            min-height: 100vh;
            flex-direction: column;
        }

        .Site-content {
            flex: 1;
        }
    </style>
</head>
<body class="Site">
<header>header</header>
<main class="Site-content">Site-content</main>
<footer>footer</footer>
</body>
</html>